Method for underpinning buildings

ABSTRACT

A method for underpinning a building comprises arranging at least one elongated supporting element below and substantially parallel to the foundation of the building. A whole side wall of the building may thus be underpinned in a single operation without unnecessarily weakening the existing underground. By coupling a plurality of elongated supporting elements, a kind of large-surface foundation that securely supports the building can be created. The architectonic substance of very old buildings may thus be preserved in a non-aggressive manner. In addition, the underpinning method can be carried out very quickly and at a relatively low cost.

This application is filed under 35 USC § 317 of PCT/DE96/01526 which wasfiled on Aug. 16, 1996.

BACKGROUND OF THE INVENTION

The invention concerns a method for underpinning buildings in accordancewith claim 1 and furthermore a method of forming reinforced-concretesupporting elements in accordance with the preamble of claim 17.

It has long been known to consolidate foundations on unstable subsoil byexcavating from under portions of the foundations and supporting thesethrough an underlying concrete or brick structure. As part of thefoundation is deprived of its support in the subsoil in the process,particularly in the case where the structure is in a state of decay,there is a risk of cracks forming in the brickwork and of the buildingcollapsing in the worst case. These works must consequently be carriedout with utmost care and are highly time-consuming.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to propose a method wherebyunderpinning of buildings may be performed speedily and safely withsimple means.

This object is attained by arranging at least one elongated supportingelement in a direction substantially parallel to the foundationunderneath the building to be underpinned.

This has the essential advantage that an entire section of a building'sfoundation may be underpinned in a single operation. Producing theelongated supporting element thus does not affect the subsoil on whichthe foundation rests to such a degree as to result in subsidences. Atthe same time, a stabilizing element for the entire side of the buildingis present underneath the foundation after completion of the elongatedsupporting element.

As a result, the time required for underpinning is reduced substantiallyas the entire section of the foundation is underpinned in one operation,other than in the previous technique wherein portions of the foundationwere underpinned piece by piece.

It is another essential advantage that the hazard of accidents toworking personnel can be reduced substantially as they will not bepresent immediately underneath the wall to be underpinned but in alateral distance from the building.

It is another advantage that the building to be underpinned is lessstrained by this method, and the risk of the brickwork developing cracksor even collapsing is diminished substantially.

It is another advantage of this method that means common inconstructional engineering and in civil engineering may be employed forits implementation. The technology necessary for carrying it out is thusavailable and comparatively inexpensive.

Further advantages can be obtained if a plurality of elongatedsupporting elements are arranged underneath the foundation and at leastpartly coupled among each other. Hereby the foundation is underpinnedstepwise and may thus increasingly be stabilised. For producing a singlesupporting element, its dimensions are selected such that the subsoilbelow the foundation is affected only to an insignificant extent. Owingto the interaction of several supporting elements the foundation is thenincreasingly supported and eventually rests securely. In this manner akind of large-surface foundation is created which has the effect of a"raft" carrying the foundation on the unstable subsoil.

Particularly by arranging supporting elements in a grid-like manner itis possible to obtain efficient underpinning of the entire building inthe case of larger structures such as churches etc. Such buildingsgenerally have a structure wherein the load of the building rests on agrid of supporting columns. These columns are partly located in the sidewalls and partly in the inner space o f the building. Due to thegrid-like arrangement of the supporting elements, it is possible toproceed by specifically supporting respective load-bearing elements.Non-aggressive underpinning of all the load-receiving points of thebuilding is therefore possible.

It is furthermore also possible to underpin single columns in the innerarea of a building if the foundation settles in one area of the buildingonly.

It is a further advantage if a system of mutually coupled supportingelements is established under the building to be underpinned. Hereforsupporting elements designed as tensile and compressional members mayspecifically be arranged and coupled to each other such as to establisha connection with a stable subsoil and receive the load of the building.

A stable design of the elongated supporting element may be achieved bycreating the individual supporting elements through introducing a boreunderneath the foundation and producing in this bore a hollow or closedrod having a circular cross-section and possibly including tensile andcompressional cables. The supporting element is thereby enabled toabsorb tensile as well as compressional forces. Particularly where thesubsoil underneath the building does not have a uniform consistency,various load conditions subject to change in the course of time must beprovided for. This makes for a strong supporting element, the loadbearing capacity of which can be increased by interaction with furthersupporting elements to thereby enable absorption of the required load.The annular configuration of the supporting element furthermore enablesintroduction of reinforcing elements and concrete in the free core area,whereby the arrangement is further consolidated. In addition it ispossible, e.g. at points of intersection under supporting elements, toinject concrete at high pressure by means of openings in the concretering, whereby the individual supporting elements are interconnected andthe space under the supporting element is filled up with concrete todisplace the loose subsoil.

As an alternative it is also advantageous to form the individualsupporting elements by introducing a bore underneath the foundation andfilling this bore with steel wire fabric and injected concrete. Thissubstantially reduces the expense in comparison with formation of theconcrete ring including tensile and compressional cables. Depending onthe application at hand, the simple method or the more expensive one maybe employed.

If the bore is created by means of an anchor boring device or atunnelling device or excavator, this has the advantage that means knowne.g. from sewer construction may be utilised. By using these means whichcreate a stable borehole in the subsoil--which particularly in the caseof the tunnelling device is furthermore compacted outwardly--the desiredbore may be created in a simple manner.

If the supporting elements are formed by introducing a bore underneaththe foundation, press-inserting pipes and filling the latter with steelwire fabric and injected concrete, then a stable bore can be createdparticularly in the case of loose subsoil such as e.g. gravel or sand.Under certain circumstances, the bore produced in these subsoils wouldcollapse very quickly even before its consolidation by means of aconcrete ring or steel concrete could be accomplished. Thus the dangerof further deconsolidation of the subsoil is reduced in this case.

This kind of bore with press-inserted pipes is advantageouslyestablished by means of a pipe pressing or shield driving method. Inother words, it is once again possible to revert to methods commonlyapplied in civil engineering.

It is a further essential advantage if bores having a vertical ordownward orientation are introduced between the margin of a supportingelement and the at least one supporting element. Hereby the subsoilunder the supporting element can be further consolidated by beingencompassed in a ring of downwardly oriented bores. The unstable subsoilthus rests on the supporting elements placed in parallel with thefoundation and on the bores having an upright orientation, or on thesteel concrete supports introduced into them, respectively.

The downwardly oriented bores are filled with concrete, preferablysteel-reinforced concrete, which is introduced in particular byhigh-pressure injection. This results in a certain displacement of theunstable subsoil underneath the foundation, and the space is filled upwith concrete. Where the subsoil cannot be displaced, it will becompacted in such a degree as to be present in a stable condition.

On the other hand, the area between the at least one supporting elementand the supporting element can be excavated and filled with concrete,preferably steel-reinforced concrete, after the downwardly orientedbores have been introduced and a support has been provided in them. Thismay equally serve to achieve stable underpinning of the load-bearingelement.

If several supporting elements are arranged in a stacked configuration,then formation of an upright wall may be achieved by coupling them amongeach other. In this manner, for example in tunnel construction, it ispossible to create a shaft between two points which is constituted ofouter walls of individual supporting elements. The soil inside the shaftcan subsequently be removed. Cellaring of already existing buildings isalso conceivable in this manner.

Forces originating in the soil and in the burden may be balanced byflooding the cavities of the supporting elements. Hereby it is possibleto effect or prevent lifting or heaving of the building according tonecessity. In the case of varying soil consistency, particularly with aview to the ground water table, the stresses acting on the building canbe balanced.

Another aspect of the invention furnishes a method whereby cavities inthe ground may be stabilised.

This is achieved by introducing a binding agent into the periphery ofthe cavity while the cavity is being created.

Hereby it is possible to remedy problems brought about by an instabilityof the bore, which occur particularly in the case of loose subsoil suchas e.g. sand or gravel, or in the presence of high water pressure. Inthis context it is an essential advantage that this consolidation may beachieved directly in connection with creating the cavity. Thus anapparatus for injecting the binding agent may be arranged directlyfollowing the boring apparatus. This makes good use of the fact that thesoil is generally present in a compacted form directly behind the end ofthe tunnelling device and will thus, at least for a short period, bedimensionally stable. Subsequent introduction of a binding agentreliably consolidates the cavity.

For this purpose one-component or multi-component binding agent may beutilised, e.g. concrete, resins, silicates or other suitable mineralsubstances, or polymers.

This is suited to substantially reduce the expenses for forming stablebores, particularly in the case of the present invention.

In accordance with a further aspect of the invention, a method offorming reinforced-concrete supporting elements is furnished.

Reinforced-concrete supporting elements are conventionally obtained bybending constructional steel elements into so-called reinforcement cagesand using wires to connect them with further reinforcing elements suchas e.g. constructional steel rods etc. The reinforcement thus producedis then placed inside formwork, i.e. an area to be filled with concrete,and embedded in concrete.

In the above described method for underpinning buildings, elongatedsupporting elements are arranged substantially in parallel with afoundation. To this end, a bore intended for receiving a reinforcementis formed underneath the area to be underpinned. The bore issubsequently filled up by pouring concrete.

Since such a bore is positioned underneath the foundation of thebuilding to be underpinned, start and target shafts have to be providedin most cases in order to produce the bore. The dimensions of start andtarget shafts are, however, generally kept small because only a minimumamount of soil should be displaced, and because the available space isin many cases restricted by adjoining buildings or the like. As aresult, the length ratio of a prefabricated reinforcement is unfavorablecompared with the space available for inserting it into the bore,whereby insertion of the reinforcement into the bore may causeconsiderable difficulties.

The formation of reinforced-concrete supporting elements can besimplified substantially by introducing single steel cables into thebore following completion of the boring process and combining them withfurther reinforcing elements during their introduction to thereby form areinforcement.

This makes it possible to continuously form the reinforcement on thesite. For this purpose the individual reinforcing elements canseparately be approached to the bore opening to thereby make use of theflexibility of the individual elements. This substantially facilitateswork in the workspace inside the shaft which is generally limited. Onlyimmediately prior to insertion into the bore, the components of thereinforcement are combined with the steel cables into a reinforcing cagewhich substantially has dimensional stability. Insertion of such areinforcement is therefore simplified substantially in comparison with aconventional, pre-fabricated reinforcement. Construction ofreinforced-concrete supporting elements can in this manner be simplifiedsubstantially particularly in the presence of unfavorable localcircumstances.

It is another advantage if, upon retracting the boring apparatus or thedrive means of the boring apparatus into the starting area followingcompletion of the bore, a hauling element, in particular a steel cable,is pulled through the bore and subsequently used to take thereinforcement, which is preferably arranged in the starting area,through the bore. Thus the operation of removing the boring apparatus orthe drive means for the boring apparatus, which is inevitable in anycase, is combined with the introduction of a hauling element which islater on used for guided introduction of the reinforcement into thebore.

In this case the reinforcement is connected to the hauling element anddrawn into the bore by it. Herein it is an essential advantage thatintroduction of the reinforcement into the bore is guided, and thatmoreover introduction by means of pulling forces may be accomplished inan essentially easier manner than insertion by pressure. The risk of thereinforcement getting hooked on the bore wall and thus of blocking isdistinctly lower.

It is in this case furthermore advantageous if the reinforcement has notbeen completed yet at its end connected to the hauling element and e.g.constitutes a conical configuration which slides through the bore withcomparative ease.

Due to the fact that the steel cable with the reinforcement fastened toit is pulled through the bore by means of a cable winch preferablyarranged in the target area, the forces required for introducing thereinforcement can be applied reliably. The progress of introduction canfurthermore be controlled in a continuous manner to thereby preventjolting etc. which may occur when the reinforcement is hooked on thebore wall e.g. upon hauling by hand.

As an alternative it is also possible to haul the reinforcement into thebore in the process of retracting the boring apparatus, or the drivemeans for the boring apparatus, respectively, into the starting area.This makes it possible to omit the introduction of a hauling elementsince the retracting motion of the boring apparatus is thus employed forintroducing the reinforcement. This further simplifies arrangement ofthe reinforcement inside the bore.

If the steel cables are connected to a spiral as they are pulled intothe bore, then the reinforcing cage can be given the desiredconfiguration. The reinforcement itself will thus remain dimensionallystable and be present in the desired locations. It is thus possible tocreate well pre-determinable reinforced-concrete supporting elementswhich in addition have accurately calculated static properties.

If the steel cables are provided in a coil form, then these coils may bearranged in the starting area such that the cables will unroll whilebeing pulled into the bore. Introduction of the steel cables into thebore thus becomes substantially easier. If the length of the steelcables inn the coil is moreover predefined, then the required space inthe starting area may be kept small.

The final concrete work may be prepared very well by jointly pulling atleast one concrete delivery hose into the bore. If the concrete deliveryhose is furthermore continuously retracted during the concrete work,smooth and well controllable filling of the bore with concrete from endto end may be achieved. The formation of cavities particularly in theupper margin between the reinforced-concrete supporting elements and thebore wall can thus essentially be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of this invention shall be explained below in moredetail by way of embodiments and reference to the drawings, wherein:

FIG. 1 is a front elevation of a building to be underpinned and of theintroduced supporting elements;

FIG. 2 is a side elevation along line I--I in FIG. 1 of the building tobe underpinned and of the introduced supporting elements;

FIG. 3 is a schematic plan view of a three-aisle church structure havingsupporting elements arranged in a grid shape;

FIG. 4 is a sectional view along the line II--II in FIG. 3 illustratingunderpinning of a load-bearing column;

FIG. 5 is a plan view corresponding to the representation of FIG. 4;

FIG. 6 is a side elevation of a building to be underpinned, with awedge-shaped arrangement of the supporting elements;

FIG. 7 is a side elevation of a building to be cellared and ofsupporting elements arranged in a stacked configuration;

FIG. 8 is a section through one embodiment of a supporting elementaccording to the invention;

FIG. 9 is a schematic representation of an interlaced large-surfacefoundation consisting of supporting elements according to the invention;

FIG. 10 is a schematic representation of a system of horizontal andvertical supporting elements;

FIG. 11 is a schematic representation of a technique for stabilizing ofvertical supporting elements;

FIG. 12 is a schematic representation of the arrangement of supportingelements in the presence of different subsoil layers;

FIG. 13 shows a detail of the insertion opening of the bore while thereinforcement is introduced in order to form a reinforced-concretesupporting element;

FIG. 14 is a representation according to FIG. 13, wherein a concretedelivery hose is introduced together with the reinforcement;

FIG. 15 shows a section through a reinforced-concrete supporting elementaccording to another embodiment of the invention; and

FIG. 16 is a sectional view of a building to be underpinned, differentsubsoil layers, distribution of the load thereon following underpinning,and a level regulating anchor and a bore for direct lifting ofbuildings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 represent a first variation of the method for underpinningbuildings. Herein a building 1 is underpinned at a foundation 2 of itsfront wall. To this end a first shaft 3 and a second shaft 4 are createdat a lateral distance from the front wall. By means of a device notrepresented here and including a tunnelling device, a bore 9 is createdbetween the first shaft 3 and the second shaft 4 at a distanceunderneath the foundation 2 of the building 1. Inside this bore 9 asupporting element 5 having the form of a concrete ring and includingtensile and compressional cables 6 is formed by concreting and by meansof suitable formwork (cp. FIG. 8).

In another embodiment the supporting element 5 may also be given theshape of a concrete rod having suitable reinforcement.

The supporting element 5 thus extends at a distance underneath thefoundation 2. The diameter of the supporting element 5 is selected suchthat creating the bore 9 will not unnecessarily destabilize the subsoilunder foundation 2. After introduction of the first supporting element5, additional supporting elements 5 are created in a lateral position.The supporting elements 5 are coupled to each other to form alarge-surface foundation acting on foundation 2 like a "raft".

The stabilising effect of this plurality of supporting elements 5 on thefoundation 2 of the front wall of building 1 possibly is alreadysufficient for preserving its structural integrity.

In addition it is moreover possible to create vertical or downwardlyoriented bores 13 from the edge of foundation 2 downward as far as thesupporting elements 5 and to inject concrete into them. Hereby it ispossible to further consolidate the subsoil under the foundation 2.

Whenever it is necessary to underpin one side of a building for thepurpose of creating an annex with a basement, i.e. having a foundationin a position essentially below the foundation of the already existingbuilding 1, it is furthermore possible to arrange a sufficient number ofhorizontal supporting elements 5 in a stacked configuration under thefoundation 2. In this way a secure support for the existing building 1may be achieved and ensured prior to excavation for the annex basement.

Underpinning of the building 1 in the described manner can be obtainedfor an existing building on one side and--if necessary--even on allsides or under the inner load-bearing walls of the building.

Another example shall serve to describe the creation of a grid ofsupporting elements 5 underneath a building 1.

FIG. 3 shows a schematic representation of a three-aisle church building10 in plan view. The static configuration of the church 10 isessentially supported by vertical supporting structure such asload-bearing elements or columns 11.

In order to underpin the church 10 as a whole, it is sensible totransfer the grid created by the arrangement of columns to thesupporting elements 5. This process shall exemplarily be explained byreferring to one column 11.

To this end, four shafts 12A-12D are excavated laterally beside thechurch 10. Starting out from these shafts 12A-12D, a plurality ofsupporting elements 5 are then created in the transverse direction ofthe nave and a plurality of supporting elements 5 in the longitudinaldirection thereof. The supporting elements 5 are, in accordance with therepresentation of FIG. 4, provided at a distance underneath the column11. A row of downwardly oriented bores 13 are then introduced into thechurch floor in the configuration shown in FIG. 5. The downwardlyoriented bores 13 extend downward from the edge of the column 11 as faras the supporting elements 5. The downwardly oriented bores 13 arecreated partly vertically and partly also in an oblique downwarddirection. Subsequently, a support is arranged in the downwardlyoriented bores 13 such as by filling the bores 13 with concrete byhigh-pressure injection, with the result that the existing subsoil willpartly or even entirely be displaced. This results in the creation of aconcrete foundation above the elements 5, which as a rule extends and ispresent in accordance with the dashed line of FIG. 5.

The downwardly oriented bores 13 may alternatively be filled up frombelow by injecting concrete into the horizontal bores 9 for thesupporting elements 5. This results in a good connection betweenhorizontal and downwardly oriented bores.

The column 11 is thus underpinned and securely supported by a concretefoundation. One proceeds analogously for remaining columns 11 of thechurch building 10, and according to necessity at the foundations of theouter walls.

In the case of particularly loose subsoil, such as e.g. sand, it ispossible, in accordance with the representation of FIG. 6, to constructthe plurality of supporting elements 5 in wedge-shaped configurationwhose point is directed downward underneath the foundation of abuilding. By adding further groups of supporting elements inwedge-shaped configuration, secure support for the building is madepossible even in this type of case because the groups of supportingelements are wedged against each other. This configuration of thesupporting elements 5 may also be transferred to other desiredapplications for underpinning buildings. Furthermore differentconfigurations of supporting elements 5 are possible according to desireand in correspondence with the requirements of a specific case.

In accordance with the representation of FIG. 7 it is possible, by meansof upright supporting elements 5 arranged in a stacked configuration andcoupled among each other, to form a wall inside the soil which enablesformation of a basement under an existing building. For this purpose theunderpinning would e.g. have to be implemented as a wall having asufficient height on three sides of the building, and on the fourth sidean adequate underpinning in the sense of a structural girder. Where thebearing plate of the existing building is capable of absorbing thestatic forces through the inner bearing walls, or is provided with anunderpinning again in the sense of a girder, respectively, the soil maybe excavated from under the fourth side of the building. Herein thesupporting elements can be arranged in one or several rows such as toresult in a type of horizontally arranged pile wall or bore pile wall.

It is understood that a basement may also be formed in another way bymeans of the supporting elements 5; in this case it is only necessary totake care that the existing building is adequately supported on thesubsoil.

FIG. 8 shows the construction of a supporting element 5 in accordancewith a first embodiment. It includes a concrete ring provided withtensile and compressional cables 6. These tensile and compressionalcables 6 absorb arising tensile forces and pressure loads, respectively.The concrete ring is created by filling up the free space between anexternal steel pipe 7 and an internal steel pipe 8 and, where necessary,finally provided with a reinforcement and filled by pouring concrete.

Instead of forming this concrete ring including tensile andcompressional cables 6 inside the bore 9 underneath the foundation 2 ofthe building 1, it is equally possible to press in pre-fabricated pipesand in turn fill these with steel wire fabric or suitably arrangedtensile and compressional cables and injected concrete.

It is furthermore also possible to fill up the entire bore 9 with asteel wire fabric and injected concrete to thus establish a rod-typesupporting element.

Depending on the loads and the consistency of the subsoil, it ispossible to revert to either the simpler method or the more expensiveone. The bore 9 itself may be created by means of an anchor boringdevice or tunnelling device, and in a case where pipes are to be pressedin, this can be achieved by means of a pipe pressing or shield drivingmethod.

Pressing in pre-fabricated pipes is recommendable particularly in thecase of very loose subsoil such as e.g. sand or gravel in which it isvery difficult to create a dimensionally stable bore.

Where loose subsoil or high water pressure in the ground is involved, itis furthermore useful to introduce a binding agent into the peripheralwall of the bore 9 in order to consolidate the bore while the tunnellingdevice progresses. This injection of binding agent may be effected instar-shaped propagation immediately behind the drive means for theboring apparatus. Suitable binding agents are concrete, resins or thelike. The expense for forming the bore 9 is thereby reducedsubstantially.

This method for consolidation of a bore or cavity in the ground may alsobe transferred at will to other applications such as e.g. tunnelconstruction.

In hard, e.g. rocky subsoil, the bore 9 may also be accomplished bysinking.

It is furthermore possible to arrange the supporting elements 5 inseveral horizontal planes cross-wise underneath each other. Each planethen includes a plurality of adjacent supporting elements 5. Arrangingrespective equidirectional planes in a staggered formation increases thelarge-surface foundation effect.

As the technology for steering the boring apparatus is available, it ispossible--particularly in the case of underpinning large-surfaceareas--to arrange a plurality of supporting elements 5 interlacingly inaccordance with the representation of FIG. 9. This has the effect thatthe large-surface foundation thus formed is consolidated in itself byinterlocking and is capable of better receiving the loads.

The described configuration of supporting elements 5 arranged in astacked configuration can moreover be employed in tunnel construction.

The air contained in the cavity of a supporting element according toFIG. 8 may furthermore be utilised, e.g. in the case of wet subsoil, togenerate upward hydraulic pressure. The hollow supporting element 5 thushas the tendency of "floating" on the groundwater table, which may evenmake it possible to lift buildings. In order to achieve this, additionalbuoyant bodies may also be arranged e.g. in the area of the lateralshafts. This results in a "floating foundation" stabilising thebuilding.

Where e.g. the groundwater table is subject to seasonal variations, orif the upward pressure of the supporting element 5 should turn out to beexcessively high, a uniform behavior of the underpinning can be achievedby controlled flooding of the cavity inside supporting element 5. Thebuilding will thus not be subjected to variable stresses due to avarying consistency of the subsoil.

In accordance with the representation of FIG. 10 it is possible toconstitute a system of supporting elements 5 in the sense of a "floatingbearing" underneath a building to be underpinned to obtain securesupport for the building 1.

In accordance with the representation in the figure, a building 1 standson unstable subsoil 20, e.g. peat, clay, sand or the like, with a stablebase layer 21, e.g. rock, provided underneath. The building 1 is in thisrepresentation indicated by only three bearing points 22, 23 and 24representing the foundations of the building.

In order to support the building, initially a first compressionalelement 25 is arranged horizontally in the area of bearing points 22, 23and 24. A first tensile element 26 is passed through underneath thebearing points 22, 23 and 24 and anchored on one side in the stable rocklayer 21. The other side of the first tensile element 26 is supported onthe stable rock layer 21 by means of an upright supporting elementhaving the form of a pillar 27.

The tensile and compressional elements may have the form of a singlesteel cable or an arrangement of several steel cables, or areinforcement embedded in concrete.

Further tensile elements 28 and 29 are passed through under the bearingpoints 22, 23 and 24. Herein a tensile element 28 in accordance with therepresentation of FIG. 10 can pass underneath a single bearing point 22or several bearing points 23 and 24 as is indicated for tensile element29. In the latter case the tensile element can be returned to thesurface by steering the boring apparatus between the bearing points.

The additional tensile elements 28 and 29 are supported on the stablebase layer 21 or on the first tensile element 26 by means of furthercompressional elements 30-34. The tensile elements 26, 28 and 29 aretensioned and the bearing points 22, 23 and 24 of the building 1 aresupported.

The upright compressional elements 31-34 are placed e.g. directly on thefirst tensile element 26 or on a plurality of first tensile elements 26to obtain a stable base.

FIG. 11 shows how horizontal and upright supporting elements may becoupled to each other to prevent shifting or toppling. E.g., twosupporting elements each having a substantially horizontal orientationencompass one upright supporting element in one region thereof from twodifferent directions. This encompassing relation may be repeated in alocation spaced apart from the first one to thereby restrict movement ofthe upright supporting element. The upright supporting element is thusheld tightly and wedged between the horizontal supporting elements.

FIG. 12 shows how the supporting elements 5 of the invention may in thepresence of different subsoil layers be employed e.g. under a concretebearing plate 37 for the purpose of stabilizing the subsoil. Herefor abore 9 alternatingly passing through the respective subsoil layers iscreated by means of a steered boring apparatus. Particular in cases ofe.g. a gravel layer 38 and a clay layer 39 intermingled by erosion,consolidation may be obtained in this manner.

The technique for creating a reinforced-concrete supporting elementshall now be explained in more detail.

Initially a bore 9 is created, e.g. by means of a tunnelling device. Thetunnelling device, which is not represented in the figures, is setinside the starting area 3 and moved toward the target area 4 by a drivemeans such as to form a bore 9 which is stable inasmuch as the soil isdisplaced. In the target area 4 the head of the tunnelling device isremoved and the drive means is eventually retracted into the startingarea 3.

Prior to retracting the drive means of the tunnelling device, however, ahauling element, such as steel cable 16 is fastened to the latter, whichis thus in turn pulled through the bore 9. The steel cable 16 is paidout by a cable winch positioned in the target area 4, which is notrepresented in the figures. After the steel cable 16 has arrived in thestarting area 3, the drive means for the tunnel excavator is removedfrom the starting area 3.

In the starting area 3 several cable drums are positioned, of which onlyone respective cable drum 18 is represented in FIGS. 13 and 14. Steelcables, of which only four cables 6 are represented in FIGS. 13 and 14,are wound on these cable drums. The steel cables 6, just like thefurther steel cables not represented here, are fastened to the steelcable 16. A spiral 14 of construction steel is arranged around the steelcables 6 and in a known manner combined with the steel cables atpredetermined distances, whereby the desired shape of the reinforcementwire cage is achieved. The ends of the steel wires 6 are left free suchthat they will assume a conical configuration upon mounting to the steelcable 16. The risk of the reinforcement getting hooked while beinghauled into the bore 9 is thereby reduced substantially.

The spiral 14 is fastened in the starting range of the steel cables 6.While the reinforcement 15 thus formed is drawn into the bore 9, thespiral 14 is continuously fastened to the steel cables 6 which are againfreely provided in front of the opening of bore 9.

In this manner the reinforcement 15 is constituted continuously on thesite and hauled stepwise into the bore 9.

After the reinforcement 15 has reached the end of bore 9 in the targetarea 4, the ends of steel cables 6 are separated from the steel cable16. These ends of the steel cables 6 are then fashioned to form thedesired reinforcement 15 with the spiral 14. As a result, thereinforcement 15 is provided in the desired configuration over theentire length of the bore 9.

In accordance with the representation of FIG. 14, a concrete deliveryhose 17 is also pulled into the bore 9 together with the steel cables 6and is thus provided at the end of bore 9 in the area of the target area4. The opening of bore 9 in the target area 4 may now, if necessary, beclosed by formwork, followed by filling the bore 9 with concrete. Tothis end, concrete is introduced into the bore 9 through the concretedelivery hose 17. The concrete delivery hose 17 is in the processcontinuously retracted towards starting area 3 in accordance with thequantity of supplied concrete. Complete filling of the bore 9 is therebyobtained in each area underneath the foundation 2 of the building 1.

If necessary, a supplementary pressure hose may furthermore jointly beintroduced into the bore 9 to enable a concrete pressure ensuringcomplete filling of bore 9.

The concrete work is continued until substantially the entire area hasbeen filled with concrete as far as starting area 3.

After setting there is provided a reinforced-concrete supporting elementwhich is suited as an underpinning for a building 1 having a weakenedstructural substance. The form of the reinforced-concrete supportingelement 5 corresponds to the representation of FIG. 15. This formincluding arranged steel cables in a ring permits e.g. good absorptionof tensile and compressional forces at a right angle to the maindirection of the reinforced-concrete supporting element 5.

It is possible to not only support load-bearing walls of buildings inthis manner, but for example also to reform insufficiently reinforcedbearing plates of industrial structures etc. Such reinforced-concretesupporting elements may furthermore be used to form or subsequentlyreform basement walls and basement floor plates under existingbuildings, for which purposes start and target shafts having onlyrelatively small dimensions are required.

As it is possible to keep the dimensions of start and target shaftssmall, and as additional excavation works underneath the buildings arefurthermore not required, it is not necessary to perform large-volumelowering of a high groundwater table. Merely the start and target shaftmust be formed such as to be substantially free of ground water.

Since the reinforcement for the reinforced-concrete supporting elementsis formed immediately on the site, pre-fabricating it is not necessary.In addition, those difficulties are avoided which would result from thelow flexibility of such a pre-fabricated reinforcement during itsintroduction around a corner through a narrow shaft into a horizontalbore in the soil.

Besides the aspects demonstrated above, the invention permits furtherpossible approaches to configuration.

The proposed method can in principle be employed whenever any kind ofsteel concrete element is to be formed between a starting and targetpoint. This is not limited to bores but is also applicable e.g. toopen-top formwork.

In this manner it is also possible to form pipe-shapedreinforced-concrete supporting elements if a different formwork is usedfor the core.

It is furthermore possible to draw the reinforcement into the bore 9 byusing the retracting movement of the drive means for the tunnellingdevice. In this case, however, the drive means for the tunnelling deviceis tied up at this site for a certain period of time, i.e. untilformation of the reinforcement, and is not available at anotherlocation.

The number of steel cables used in forming the reinforcement may bevaried as desired, and in certain cases only a single steel cable mighteven be sufficient. The type of additional reinforcing elements is notlimited to the spiral 14 mentioned here, but different elements such asconstruction steel cages e.g. including construction steel fabrics orthe like may also be employed. Instead of the spiral 14, ring elementsare also partly utilised in practice, which are more suitable in certainexceptional cases. As a rule, however, they do not provide the highrigidity and load-bearing capacity as in the case of the spiral. Thespiral 14 may furthermore be arranged either externally or internally ofthe steel cables.

It is furthermore possible to introduce not only one concrete deliveryhose into the bore, but a desired number of concrete delivery hosesdepending on the bore diameter or the available free space.

Application of the method of the invention is furthermore not restrictedto horizontal reinforced-concrete elements, but is also possible e.g.for formation of vertical supporting columns in old walls, orconsolidation of soil or rock formations.

The steel cables wound on the cable drums may have any desired length orbe adapted beforehand to the desired length. In addition it is, ofcourse, possible to omit the cable drums and supply the cables singlyfrom the upper edge of the shaft.

The steel cables 6 are combined to form a reinforcement 15 with theadditional reinforcing elements in a manner known per se. This may beachieved by connection through wires, i.e. production of wire mesh, ore.g. by welding the reinforcing elements to each other.

Static analysis of the underpinning of the invention may be carried outby combining the known static analysis methods for the bored pile walland for the large-surface foundation. The configuration of thesupporting elements, e.g. in accordance with FIG. 7, may be treated inthe sense of a horizontally arranged bored pile wall, such thatcalculation is possible with few modifications. The results may beapplied to the invention in a meaningful manner in combination withresults from a calculation method similar to that for the large-surfacefoundation. Underpinning of buildings can thus be carried out based onan accurate static analysis.

The invention thus proposes a method for underpinning buildings whereinat least one elongated supporting element 5 is arranged substantially inparallel with the foundation 2 of the building 1 underneath the building1 to be underpinned. A whole side wall of the building 1 can thus beunderpinned without unnecessarily weakening the existing subsoil Bymutually coupling a plurality of elongated supporting elements 5, a kindof large-surface foundation can be created that securely supports thebuilding 1. The architectonic substance of very old buildings may thusbe preserved in a non-aggressive manner. In addition, the process can becarried out very quickly and at relatively low costs. Moreover theresistance of buildings against earthquakes may in this manner bestrengthened in the sense that shock waves are attenuated by means ofwater filled cavities in the solid subsoil.

It is furthermore shown how a reinforced-concrete supporting element canbe obtained in a simple manner. Herefor the construction steelreinforcing elements are joined together immediately on the site andsubsequently are gradually inserted into the area to be filled withconcrete. This makes use of the greater flexibility of the singlereinforcing elements as compared to the rigid arrangement of thepre-fabricated reinforcement, to ensure particularly in restrictedlocations that the reinforcement can be introduced in a defined mannerinto the area to be filled with concrete. It is thus possible to formaccurately defined reinforced-concrete elements having the desiredproperties.

In accordance with the representation of FIG. 16 it is possible to drillthrough the margin of the propagation zone of the foundation loadwithout any danger to buildings. It is advantageous to perform this inthe vicinity of the layer which is prone to settling, whereby thesurrounding ground area is also solidified upon subsequent injection ofbinding agent into the bore. As a result, the load propagation angle isreduced and the building rests more stably. For injecting in order tosolidify the bores, which may furthermore be reinforced with perforatedpolyethylene (PE) pipes, different pressures (up to 200 bar arecurrently available) may be employed. For example in FIG. 13, the boreis plotted as an underpinning bore in a central position under thefoundation 2. At corresponding pressures during injection, thefoundation may even be lifted. This is achieved in a controlled mannerby introducing vertical anchors which will admit the corresponding liftby slacking.

I claim:
 1. A method for underpinning a building comprising the step ofarranging at least one elongated supporting element underneath afoundation of said building, wherein said foundation extendshorizontally beneath at least a portion of said building and whereinsaid at least one elongated supporting element is arranged substantiallyparallel to the foundation of said building with a space providedbetween said foundation and said at least one elongated supportingelement.
 2. The method according to claim 1, further comprising the stepof arranging a plurality of elongated supporting elements underneath thefoundation of said building wherein at least two of plurality of saidelongated supporting elements are coupled to each other.
 3. The methodaccording to claim 2, further comprising the step of arranging saidplurality of elongated supporting elements so as to form a grid.
 4. Themethod according to claim 3, further comprising the step of arrangingsaid plurality of elongated supporting elements so as to position atleast one point of intersection of said grid underneath a verticalsupporting structure of said building.
 5. The method according to claim4, further comprising the steps of forming a second bore in a downwardorientation, arranging a support in said second bore, wherein saidsecond bore is formed between the margin of said vertical supportingstructure and said at least one elongated supporting element.
 6. Themethod according to claim 5, further comprising the step of forming saidsupport in said second bore by injecting concrete into said second bore.7. The method according to claim 5, further comprising the steps ofexcavating an area between said at least one elongated supportingelement and the foundation of said building, and filling said area withconcrete.
 8. The method according to claim 2, further comprising thestep of arranging said plurality of elongated supporting elements in astacked configuration.
 9. The method according to claim 1, furthercomprising the step of forming said elongated supporting element byintroducing a first bore underneath the foundation of said building, andby producing a concrete ring or concrete rod within said first bore. 10.The method according to claim 9, further comprising the step of creatingsaid first bore by using an anchor boring device or a tunneling device.11. The method according to claim 1, further comprising the step offorming a cavity in said at least one elongated supporting element andflooding said cavity with concrete.
 12. The method according to claim 1,further comprising the step of lifting said building and correcting astructural imbalance of said building.
 13. A method for forming areinforced-concrete supporting element, comprising the steps of:forminga bore underneath a foundation of a building, wherein said bore isformed by moving a boring apparatus from a starting area to a targetarea, wherein said bore is arranged substantially parallel to thefoundation of said building and does not impact either said building orthe foundation of said building, introducing at least one steel cableinto said bore, and forming said reinforced-concrete supporting elementinside said bore by combining said steel cable with a supportingelement, wherein said starting area and said target area are locatedbeyond the foundation of said building.
 14. The method according toclaim 13, further comprising the steps of retracting said boringapparatus into the starting area and pulling said at least one steelcable and said supporting element through said bore, wherein said atleast one steel cable and said supporting element is pulled through saidbore using a hauling element.
 15. The method according to claim 13,further comprising the step of fastening said at least one steel cableto said supporting element, and pulling said at least one steel cableand said supporting element to said target area, wherein said at leastone steel cable and said supporting element are pulled through said boreusing a cable winch located in said target area.
 16. The methodaccording to claim 13, further comprising the step of pulling said atleast one steel cable and said supporting element to said starting areathrough said bore, wherein said at least one steel cable and saidsupporting element are pulled by said boring apparatus.
 17. The methodaccording to claim 13, further comprising the step of combining said atleast one steel cable with said supporting element so as to form aspiral.
 18. The method according to claim 13, further comprising thestep of providing said at least one steel cable in the form of a coiland unwinding said coil as said at least one steel cable is beingintroduced into said bore.
 19. The method according to claim 13, furthercomprising the steps of:introducing a concrete delivery hose into saidbore, pulling said hose along with said at least one steel cable andsaid supporting element, and filling said bore with concrete throughsaid hose.
 20. A method for underpinning a building having a foundationthat extends horizontally beneath at least a portion of said building,the method comprising the steps of:arranging at least one elongatedsupporting element in a section of ground underneath said foundation andsubstantially parallel to said foundation, and wherein said arrangingstep further comprises providing a space between said at least oneelongated supporting element and both said foundation and said building,said at least one elongated supporting element thereby reinforcing thesection of ground underneath said foundation.
 21. The method accordingto claim 20, further comprising the step of arranging a plurality ofelongated supporting elements underneath the foundation of said buildingwherein at least two of plurality of said elongated supporting elementsare coupled to each other.
 22. The method according to claim 21, furthercomprising the step of arranging said plurality of elongated supportingelements so as to form a grid.
 23. The method according to claim 22,further comprising the step of arranging said plurality of elongatedsupporting elements so as to position at least one point of intersectionof said grid underneath a vertical supporting structure of saidbuilding.
 24. The method according to claim 23, further comprising thesteps of forming a second bore in a downward orientation, arranging asupport in said second bore, wherein said second bore is formed betweenthe margin of said vertical supporting structure and said at least oneelongated supporting element.
 25. The method according to claim 24,further comprising the step of forming said support in said second boreby injecting concrete into said second bore.
 26. The method according toclaim 24, further comprising the steps of excavating an area betweensaid at least one elongated supporting element and the foundation ofsaid building, and filling said area with concrete.
 27. The methodaccording to claim 21, further comprising the step of arranging saidplurality of elongated supporting elements in a stacked configuration.28. The method according to claim 20, further comprising the step offorming said elongated supporting element by introducing a first boreunderneath the foundation of said building, and by producing a concretering or concrete rod within said first bore.
 29. The method according toclaim 28, further comprising the step of creating said first bore byusing an anchor boring device or a tunneling device.
 30. The methodaccording to claim 20, further comprising the step of forming a cavityin said at least one elongated supporting element and flooding saidcavity with concrete.